不，JavaScript不是静态类型语言。有时可能需要手动检查函数体中的参数类型。

使用typeof或instanceof:

const assert = require('assert');

function myFunction(Date myDate, String myString)
{
    assert( typeof(myString) === 'string',  'Error message about incorrect arg type');
    assert( myDate instanceof Date,         'Error message about incorrect arg type');
}

看看来自Facebook的新Flow库，“一个静态类型检查器，旨在发现JavaScript程序中的类型错误”

定义:

/* @flow */
function foo(x: string, y: number): string {
  return x.length * y;
}
foo('Hello', 42);

类型检查:

$> flow
hello.js:3:10,21: number
This type is incompatible with
  hello.js:2:37,42: string

下面是如何运行它。

TypeScript是目前最好的解决方案之一。

TypeScript通过向语言中添加类型来扩展JavaScript。

Typescript版本演示

// type alias
type myDateType = Date;
type myStringType = string;

function myFunction(myDate: myDateType, myString: myStringType) {
  // do stuff
  console.log(`myDate =`, myDate);
  console.log(`myString =`, myString);
}

myFunction(new Date(), 'TypeScript is awesome!');

试试这个在线游乐场

refs

https://www.typescriptlang.org/

不，相反，你需要根据你的需要做这样的事情:

function myFunction(myDate, myString) {
  if(arguments.length > 1 && typeof(Date.parse(myDate)) == "number" && typeof(myString) == "string") {
    //Code here
  }
}

虽然不能将类型通知JavaScript语言，但可以通知IDE，因此可以获得更有用的自动补全。

这里有两种方法:

Use JSDoc, a system for documenting JavaScript code in comments. In particular, you'll need the @param directive: /** * @param {Date} myDate - The date * @param {string} myString - The string */ function myFunction(myDate, myString) { // ... } You can also use JSDoc to define custom types and specify those in @param directives, but note that JSDoc won't do any type checking; it's only a documentation tool. To check types defined in JSDoc, look into TypeScript, which can parse JSDoc tags. Use type hinting by specifying the type right before the parameter in a /* comment */: This is a pretty widespread technique, used by ReactJS for instance. Very handy for parameters of callbacks passed to 3rd party libraries.

打印稿

对于实际的类型检查，最接近的解决方案是使用TypeScript，它是JavaScript的超集。这里是5分钟内的TypeScript。